Microparticulate diets for larval and small juvenile fish pose specific challenges for aquaculturists. Microparticulate diets, by definition, have a very high specific surface area, making them vulnerable to the effects of oxidation and hydration. Many of the diet components are often labile and hygroscopic, which further exacerbates the problem. Fine, hygroscopic particles tend to clump and cake together, and adhere to surfaces with which they come in contact, making rationing and delivery difficult to achieve by automation. See, e.g., Michael B. Rust, “The Challenges of Feeding Microparticulate Diets to Larval Fish”, The Advocate, February 2000, pages 19-20, and Juan P. Law, et al, “Co-feeding microparticulate diets with algae: toward eliminating the need for zooplankton at first feeding in larval red drum”, Aquaculture, 188, (2000) pages 339-351, both of which are incorporated herein by reference.
The digestive system of larval fish is slow to develop; so artificial diets fed to them must have a high leaching rate in order to make nutrients available to the larvae that ingest the diets. This high leaching rate is a two-edged sword, in that upon contact with the water, nutrients are often lost to solution before the larvae can ingest them. Larval fish also have no body energy reserves to call upon and so they require a constant stream of available nutritive feed. To circumvent this problem, culturists often employ a technique called, “feeding the water”, where feed is delivered in pulses to excess. The feed is either eaten, falls to the bottom of the tank, or is cleared by the exchange of circulating water in the tank. This technique unfortunately creates an alternating feast and famine situation that is conducive to neither good nutrition nor good hygiene.
Small juvenile fish have a digestive system and some reserves, however they still require frequent feeding, and accurate rations. Feeding early juvenile fish can be prohibitively expensive in terms of husbandry labor. Most of this labor is rationing and feeding. Accuracy of ration is paramount in diet trials, where growth and feed conversion are correlated to the diet actually consumed by the fish; therefore feeding the water will not work. An accurate ration is calculated based upon what the fish can be expected to eat in one feeding, and must be precisely delivered for a diet trial experiment to succeed.
Prior Art automated fish feeders can be categorized by a few basic groups:                Belt feeders, generally employ a slow moving, spring wound clock powered, conveyor belt that dumps the feed off the belt as it is rolled up over the tank. An example of such a feeder is the Ziegler Belt Feeder, manufactured by Zeigler Bros., Inc. of Gardners, Pa. See, e.g., Ziegler Belt Feeders brochure (Zeigler Bros., Inc., Gardners, Pa.) Sep. 4, 2009, incorporated herein by reference        Drum feeders employ a rotating drum filled with feed and capture a small aliquot for feeding and dispenses it with each rotation. An electric clock motor usually powers this type of feeder. An example of such a feeder is the Lifegard Aquatics Intellifeed Aquarium Fish Feeder, made by Lifegard Aquatics of Cerritos, Calif. See, e.g., Intellifeed Aquarium Fish Feeder operating instructions, (Lifegard Aquatics, Cerritos, Calif.), incorporated herein by reference.        Shear feeders use some method of sliding the feed off of a base and over an edge to drop into the fish tank. This type of feeder also includes screw feeders and dial feeders, which have individual rations in separate chambers, arranged radially on a disk. The disk rotates, powered by a synchronous AC clock motor and the feed drops as it is slid over a hole in the base. An example of a screw-type feeder is the Eheim 3582 Automatic Feeder by EHEIM GmbH & Co. KG of Deizisau, Germany. An example of a dial-type feeder is the Fish Mate F14 by Ani Mate Inc., of Conroe, Tex. See, e.g., EHEIM 3582 Automatic Feeder User Manual (EHEIM GmbH & Co. KG of Deizisau, Germany), January 2008 and Fish Mate F14 Instructions (Ani Mate Inc., Conroe, Tex.), both of which are incorporated herein by reference.        Vibrating feeders use a hopper with a narrow annular opening, allowing the feed to drop when the unit is vibrated. An example of a vibratory feeder is the Sweeney Model AF6 Vibratory Feeder by Sweeney Feeders of Boerne Tex. See, e.g., Sweeney Aquaculture Feeders brochure (Sweeney Feeders, Boerne Tex.), incorporated herein by reference.        
There are a number of Prior Art Patents relating to various fish feeders. The following is a summary of a number of those Prior Art Patents.
Belloma, U.S. Pat. No. 6,715,442, issued Apr. 6, 2004, and incorporated herein by reference, discloses a fish feeder having inner and outer trays, which move relative to one another, to dispense fish feed using gravity. Belloma discloses using a pneumatic actuator to power the device.
Patterson, et al., U.S. Pat. No. 6,571,736, issued Jun. 3, 2003, and incorporated herein by reference, discloses a fish feeder for use with moist fish feed. The moist feed disclosed are pellets, of the type used with fish farming. A blower is used to direct the fish pellets towards a fish pen through a nozzle attached to the device.
Lin, U.S. Pat. No. 6,192,830, issued Feb. 27, 2001, and incorporated herein by reference, discloses an underwater fish feeder than uses compressed air. Compressed air is used to eject fish feed from a remote fish feed holder.
Halford, U.S. Pat. No. 6,082,299, issued Jun. 4, 2000, and incorporated herein by reference, discloses an automatic fish feeder using a screw-type mechanism to eject fish feed from a hopper, which then falls into the fish tank.
Evans et al., U.S. Pat. No. 5,709,166, issued Jan. 20, 1998, and incorporated herein by reference, discloses a refrigerated automatic fish feeder.
Flahs, I I, U.S. Pat. No. 5,353,745, issued Oct. 11, 1994, and incorporated herein by reference, discloses an Aquaculture system and methods for using same. A feeding hopper (FIG. 5) is used to gravity feed the diet to the tank. A gas ejector 110 is used to spread the feed over the surface.
Masopust, U.S. Pat. No. 5,199,381, issued Apr. 6, 1993, and incorporated herein by reference, discloses an automatic fish feeder using a rotating disc.
Newton et al., U.S. Pat. No. 5,072,695, issued Dec. 17, 1991, and incorporated herein by reference, discloses an automatic fish feeder using a rotating wheel.
Smelzer, U.S. Pat. No. 4,628,864, issued Dec. 16, 1986, and incorporated herein by reference, discloses an automatic fish feeder, which is water-driven. A water-filled container drives a rotating arm.
Olsen et al., U.S. Pat. No. 4,429,660, issued Feb. 7, 1984, and incorporated herein by reference, discloses a Water Powered Fish Feeder. As with Smelzer, water drives a lever arm to dispense fish feed.
Molinar, U.S. Pat. No. 4,399,588, issued Aug. 23, 1983, and incorporated herein by reference, discloses an automatic fish feeder and orienter. This device actually orients individual fishes for feeding.
Suchowski, U.S. Pat. No. 4,089,299, issued May 16, 1978, and incorporated herein by reference, discloses an air-operated fish feeder. This device, which is immersed in a fish tank, is operated by air pressure, apparently from an aquarium pump.
Hoday et al., U.S. Pat. No. 3,738,328, issued Jun. 12, 1973, and incorporated herein by reference, discloses a Fish Feeder for an aquarium, which is driven by a clock motor.
Sanders, U.S. Pat. No. 3,717,125, issued Feb. 20, 1973, and incorporated herein by reference, discloses an automatic feeder for a fish aquarium. A piston slides a rod, which takes feed from a hopper and passes it to the aquarium once a day.
Cook, U.S. Pat. No. 3,231,314, issued Jan. 25, 1966, and incorporated herein by reference, discloses an automatic fish feeder using a blower motor for dispensing palletized fish feed to a fish tank. A hopper dispenses fish feed to two fish tanks (FIG. 5) via two parallel discharge ducts 4 (Col. 3, lines 12-41). A reciprocating metering plate dispenses fish feed from the hopper. A blower is used to force the feed to two tanks at the same time, and to dry the ducts.
Appleton, U.S. Pat. No. 3,050,029, issued Aug. 21, 1962, and incorporated herein by reference, discloses an automatic fish feeder of the disc variety.
Smolin, U.S. Pat. No. 2,785,831, issued May 28, 1953, and incorporated herein by reference, discloses an automatic fish feeder with a rotating shaft, which dispenses a measured amount from a hopper, via gravity feed.
The Arvotec T Drum 2000 Feeder (see. e.g., Arvotec, Feeding Technology for Modern Aquaculture brochure Huutokosken Arovkala Group, Huutokoski, Finland, and Arvotec Feeder and Spreader Manual, Arvotec, Huutokoski, Finland, and Arvotec, Feeding Technology brochure, Huutokosken Arovkala Group, Huutokoski, Finland, all of which are incorporated herein by reference) discloses a hopper-type feeder with a compressed air dispersal unit. Compressed air is used to blow the feed from a chute, onto the surface of a fish tank. Note the dosing drum designs (Page 9, of the Feeding Technology Manual) and the nature of the compressed air dispersal unit (Page 9 of the Feeder and Spreader manual).
The Arvotec Feeding Technology manual also discloses the use of a centralized pipe feeding system, with a manifold and a number of pipes to feed different tanks. Each manifold may feed up to four tanks, and up to 28 tanks may be fed. It appears each manifold has a switching device to direct feed to a different tank, via a 3″ open-ended pipe. However, as with the Cook reference, this embodiment uses a blower to blow feed through large (3″) open pipes. The problem with such a design, as with Cook, the open-ended pipes above fish tanks, may harbor moisture, making such a design unsuitable, particularly for microparticulate feeds, which may cake and clog in the piping. The brochure states that the number of pipes is reduced, which makes cleaning easier. However, this seems to be an admission that runs of piping with fish feed and moisture contamination could require frequent cleaning. Moist caked-on fish feed in such pipes would be an ideal environment for the growth of bacteria, fungus, and mildew, which could in turn sicken or kill the fish or larva being fed.
To avoid this problem, Arvotec shows another “robotic” embodiment, where one or more hopper-type feeders are mounted on a monorail, which in turn is moved over a plurality of tanks to distribute the feed. The problem with this design is that the hoppers need to be refilled over time. To solve this problem, in another embodiment, long hoses are used to refill the hoppers from even larger hoppers. However, such a design results in a large number of expensive components, hoppers, blowers, hoses, and the like, adding to cost and complexity. Moreover, the hoses need to be made flexible enough to avoid interfering with the operation of the monorail. The robotic solution is rather costly and over-designed.
In another embodiment, the Arvotec Feeder shows a rotating drum feeder, where the drum rotates to measure a portion of feed (determined by cutout sizes in the drum) and when rotating, dumps these onto a dispersal plate. Compressed air is used to spray the feed over the surface of the water. In one embodiment, which is illustrated on a YouTube video, compressed air is used to disperse the fish feed pellets. From the video, as well as the product catalogs, it appears that the feeder merely dumps feed onto a plate, which in turn uses a timed charge of compressed air to spray onto the surface of a fish tank. In another embodiment, a rotary (spinner-type) spreader is used. The feeder in that embodiment is mounted above the tank, and thus does not solve the problem of moisture contaminating the fish feed.
The most common shortcoming of all these prior feeders is that they don't protect the feed from the effects of moisture and oxygen. Since most feeders dispense the feed directly above the fish tank, they subject the feed to a highly humid environment. The hygroscopic nature of larvae feeds results in feed eventually caking and accumulating on the feeder surfaces, resulting in deterioration of both the feed quality, and the accuracy and precision of the dispensed ration.
The challenge then, is to create a feeder that can repeatedly and automatically deliver a small, precise amount of a fragile and functionally difficult material, and protect the feed from the environment when not in use. It remains a requirement in the art to provide a feeder which may be used to feed multiple tanks, without the need for large tubes, as well as avoiding moisture and caking in such tubes, which would as a result, require frequent cleaning. And it remains a requirement in the art to provide such a feeder in a simple and straightforward manner that minimizes the number of components, cost, and complexity of the device.